Question: 7 rubber stamps cost $7.49. Which equation would help determine the cost of 8 rubber stamps?
There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 7 rubber stamps. We want to know the cost of 8 rubber stamps. We can write the numbers of rubber stamps as a proportion: $\dfrac{7}{8}$ We know 7 rubber stamps costs $7.49. We can let $x$ represent the unknown cost of 8 rubber stamps. The proportion of these costs can be expressed as: $\dfrac{\$7.49}{x}$ The cost changes along with the number of rubber stamps purchased, and so the two proportions are equivalent. $\dfrac{7}{8} = \dfrac{\$7.49}{x}$